The Effect of Surface-Coating Materials on the Flexural Properties and Surface Integrity of a 3D-Printed Denture Base Resin: An In Vitro Study

3D-printed denture base resins offer significant workflow advantages in denture fabrication, but may exhibit limitations in mechanical performance and surface quality. This in vitro study evaluated the effects of different surface-coating materials on the flexural properties and surface integrity of a 3D-printed denture base resin. Stereolithography-fabricated specimens were airborne-particle abraded and coated with single or double layers of four commercial glaze materials and an unpolymerized denture base resin; untreated specimens served as controls. Flexural properties were assessed utilizing an ISO 20795-1-based design, and surface morphology was evaluated using scanning electron microscopy (SEM) after 90 days of water immersion. Coating application (single versus double layers) did not significantly influence flexural strength or modulus. The control group exhibited the highest mean flexural strength. The unpolymerized resin groups performed closely to the ISO benchmark, whereas commercial coatings failed to enhance mechanical properties, occasionally reducing them below this reference value. Morphological analysis revealed surface irregularities in coatings lacking nanoparticles, whereas nanoparticle-containing coatings showed no visible surface defects after water storage. In conclusion, commercial glazes should be used with caution on 3D-printed resins due to potential mechanical compromise. The application of nanoparticle-containing coatings resulted in a stable surface topography, and unpolymerized resin coatings emerged as a feasible alternative.